The present invention relates generally to the field of location alert systems and, more particularly, to alert systems utilizing a heterogeneous collection of location-determining systems.
Smart devices, such as smart phones, are prevalent in modern culture. There are over 2 billion smart device users in the world. Smart devices are ubiquitous in everyday life, where many individuals carry a personal smart device on their person, everywhere they go. Many smart devices are built with location monitoring and tracking capabilities. Smart devices, when on a network, continuously transmit data about the current time and position using built-in communication receivers.
One location monitoring system is global positioning system (GPS). With GPS, a GPS receiver monitors multiple satellites to determine the precise position of the receiver and its deviation over time. GPS utilizes the time and known position of specialized satellites. The satellites carry stable atomic clocks that are synchronized with one another and with the ground clocks. Any drift from true time maintained on the ground is corrected daily. Each GPS satellite continually broadcasts a signal to be received by a GPS receiver. At a minimum, four satellites must be in view of the receiver for it to compute four unknown quantities (three position coordinates and clock deviation from satellite time). These coordinates may be displayed on a moving map display or recorded and used by some other system.
Smart device tracking is the ascertaining of the position or location at a certain time of a smart device, whether stationary or moving. Localization occurs either via multilateration of radio signals between several cellular towers of the network and the phone, or via GPS. To locate a smart device using multilateration of radio signals, the smart device emits a roaming signal to contact the next nearby antenna tower. Examples of smart device tracking include network-based, handset-based, SIM-based, and/or wi-fi based.